Space Telescope Imaging Spectrograph can simultaneously record the spectra of up to 50 spatially distinct locations within an extended object such as a galaxy. This is a crucial tool for the efficient mapping of a complex environment. As an example, long-slit Space Telescope Imaging Spectrograph spectra of young star clusters in the merging “Antennae Galaxies” revealed their ages, chemical compositions and velocities, and the slit was crucial for subtraction of the “sky background.” More Space Telescope Imaging Spectrograph observations of such merging galaxies are important to our understanding of what happens to galaxies when they collide with each other.